In a manufacturing process of a thin film transistor (TFT), as a material of an active layer in the TFT, a low temperature polysilicon (LTPS) thin film is commonly adopted.
Currently, during a preparation process of the TFT, an excimer laser annealing (ELA) approach is mainly adopted to form the LTPS thin film. The ELA approach mainly performs a laser beam irradiation on amorphous silicon thin film through an excimer laser having certain energy to transform the amorphous silicon into the LTPS at high temperatures using a laser beam energy. However, when the amorphous silicon is irradiated with the laser beam, all regions after irradiating is of a same temperature; therefore, a growth region of a polysilicon grain in the LTPS thin film after crystallization is random. This makes grains in the LTPS thin film be variable in size and of less uniformity, and causes a large amount of crystal boundaries in a TFT channel, which results in a large leakage current of the TFT, and further results in a unstable threshold voltage of the TFT, thus degrading a whole electrical performance of the TFT.